HIGH-ROUGHAGE RATIONS WITH OR WITHOUT MONENSIN FOR VEAL PRODUCTION. I. ANIMAL PERFORMANCE

Abstract

Eighty-four calves 11–12 wk old (88 ± 10 kg BW) were used in a 47-d trial to study the effects of two ground roughages (alfalfa and timothy), their proportions in pelleted rations (20, 40 and 60%) and addition of monensin (0 and 33 ppm) on animal performance. After the trial, the animals continued to consume the rations until they reached a slaughter weight of 185 kg. Calves fed rations containing timothy showed higher dry matter (DM) and digestible energy (DE) intake and higher average daily gains (ADG) than calves fed rations containing alfalfa, which was partially due to the quality of the protein used to supplement the timothy rations. Proportion of roughage did not affect DM intake with the exception of 60% alfalfa rations which had the lowest intake. Increasing the roughage in the rations reduced DE intake and ADG, and increased feed conversion values (FC), particularly at 40 and 60%. Monensin increased DE intake and FC of rations containing 40 and 60% timothy, but had no effect on DM intake or ADG. Monensin increased DE conversion values when roughages were added at levels of 40 and 60%, the effect being greater with timothy. Dressing percentage of carcasses decreased with increasing levels of roughage in the ration, the lower values being obtained with timothy. Carcass classification and color of the meat were unaffected by the treatments. Key words: Alfalfa, timothy, roughage level, monensin, calf